The proposed research is designed to study certain of the biochemical and physiological processes that are fundamental to the maintenance of a normally functional cornea. In order that the tissue be transparent a constant level of hydration must be maintained in the stroma, and this necessitates the continuous active extrusion of water across the endothelium. Accordingly, the metabolism of this cell layer will be investigated, with particular emphasis on the mechanisms by which anions may be transported from the stroma to the aqueous humor. In order that the integrity of the epithelium be maintained constant replacement of cells lost by desquamation is necessary. This replication requires considerable metabolic activity which is dependent on substrates derived almost entirely from the aqueous humor. Therefore, the mode of entry of substrates into the cornea will be studied. This knowledge will allow assessment of the adequacy of nutrient sources under conditions of deprivation or excessive demand.